The invention relates to a light-transmitting pane for displaying an image of a head-up display for polarized sunglasses. The invention further relates to a head-up display arrangement and to a vehicle having such a head-up display arrangement.
Head-up display arrangements can be used in vehicles for displaying information. A head-up display arrangement includes an image generating device for generating a virtual image and a light-transmitting pane for displaying the image. The head-up display arrangement thereby makes it possible to display information for a driver directly on the windshield of a vehicle. For this purpose, the image generating device generates rays of light in the direction of the windshield, which rays of light are reflected on the windshield in the direction of the driver. In this case, s-polarized light exhibits particularly good reflection properties. In the case of s-polarized light, the image generating device generates the light in an almost perpendicularly polarized manner with the respect to the plane of incidence on the windshield.
It is disadvantageous that the s-polarized light reflected at the windshield can only be perceived to a very limited extent or not at all by way of sunglasses which have a polarization filter. The lenses of these so-called polarized sunglasses are generally light-transmitting for p-polarized light, i.e. light that is polarized in a parallel manner with respect to the plane of incidence of the windshield.
In order to be able to read a full-color image from a head-up display arrangement by way of polarized sunglasses, additional measures are required with respect to the light-transmitting pane, particularly the windshield or combiner pane, of the head-up display arrangement. Although solutions exist for monochrome head-up displays, these cannot be used for full-color displays.
It is desirable to indicate a light-transmitting pane for a head-up display arrangement, on which the light generated by an image generating device of the head-up display arrangement is reflected and can be clearly seen by way of polarized sunglasses. Beyond that, it is desirable to indicate a head-up display arrangement which makes it possible to reflect the light generated by an image generating device of the head-up display arrangement on a light-transmitting pane and to clearly see it by way of polarized sunglasses. Furthermore, a vehicle is to be indicated that has such a head-up display arrangement.
According to a conceivable embodiment, a light-transmitting pane for a head-up display arrangement for displaying an image visible by way of polarized sunglasses includes a cholesteric liquid-crystal layer arrangement which is arranged in the interior of the pane or is arranged on a surface of the pane. An embodiment of a head-up display arrangement includes a light-transmitting pane of the above-mentioned type as well as an image generating device for generating an image by way of rays of light generated on the output side. The pane and the image generating device are arranged such that the light generated by the image generating device impinges on the cholesteric liquid-crystal layer arrangement.
The cholesteric liquid-crystal layer arrangement can be applied directly to the glass, which can be used as the substrate in this embodiment. According to a further embodiment, the cholesteric liquid-crystal layer arrangement can be applied to a polymer film substrate and be glued onto a surface of the light-transmitting pane or be integrated in the interior of the pane. When the pane is a windshield or a combiner pane of a vehicle, onto which the cholesteric liquid-crystal layer arrangement is glued, light generated by the image generating device on the output side in a circular or p-polarized manner, when impinging on the cholesteric liquid-crystal layer arrangement, is reflected in a circularly polarized manner in the direction of the driver. The p-polarized light fraction of the circularly polarized light is transmitted by polarized sunglasses and, for the wearer of the sunglasses, results in a visible image generated by the head-up display. When the cholesteric liquid-crystal layer arrangement is arranged in the interior of the pane, although the p-polarized light fraction directed to the driver is changed because of the air-glass boundary layer of the pane, so that elliptically polarized light is reflected in the driver's direction, depending on the selected polarization of the impinging light, the p-polarized light fraction of the reflected light will still always be sufficiently large in order to be perceived by a wearer of the polarized sunglasses.
In the following, the invention will be explained in detail by means of figures, the embodiments of the light-transmitting pane, the head-up display arrangement and the vehicle having such a head-up display arrangement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.